Controllable grid leak



March 13, 1928. 1, 25

A. PRESS CONTROLLKBLE GRID LEAK Filed June 25. 1920 wnussszs; INVENTOR fibre/2am Press I ATTORNEY Patented Mar. 13; 1928.

UNITED STATES I 1,662,510 PATENT 0F ABBAH AM PRESS, OF WILKINSB URG, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTBICk MANUFACTURING COMPANY, A COBIORATION OF PENNSYLVANIA.

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Application filed June '25, 1920. Serial a... 391,648.

This invention relates. to wireless telegraphy and particularly to grid-condenser circuits of triodes, audit has, for one of its principal objects, the 1)rovision of a control for such condenser circuits.

In the art of wireless telegraphy, it has difliculty encountered with such discharge resistances, preferably of the non-reactive type, has been their great fra ility and, especially,-their inconstancy. The present invention, therefore, contemplates, as one of its features, the provision of a grid-leak controlling means which shall be practicably invariable and, furthermore, onethat shall combine, as far as possible, all the soft-tube requirements of the De Forest conductive ionization and still retain the advantages of a hard tube. 7

Other features of my invention will ob viously follow from an inspection of the drawings when taken in conjunction with the accompanying description.

Figure 1 is acdiagram illustrating a pre ferred embodiment of my invention in which a soft-tube control is placed across the gridfilament connections of a hard triode.

Fig. 2 is a diagram illustrating an alternative form of my invention, wherein the control element is merged with the triode grid.

Figs. 3 and 4 are diagrams illustrating alternative arrangements of hard-tube controls for triode circuits.

In the usual receiver circuit, a variable grid condenser 1 is connected, on the one side, to the grid 2 of a triode 3, and, on the other side, to a coupling coil 4. Shunted across the coupling coil 4 is a condenser '5 to co-operate therewith as a part of an canalization which includes the lead 6 attached to the filament 7 of the triode. The filament 7 is excited in the usual manner by means of an adjustable battery connection 8. The

plate-9 of the triode is, moreover, connected also usual to shunt the telephpne and its associated battery with a condenser 12.

The soft-tube control element 13 of my invention, as shown in Fig. 1, is connected in FICE'i shunt with the grid-filament circuit of the hard-vacuum type of triode 3. The filament 7 of the grid control is fed by a battery 14,

one pole of which is connected to the lead 6,-

whereas the plate 15' of the control is con- 7 nected to the grid element 2. In the type of circuit shown in Fig. 1,the two separate functions present in the De Foresttype of circuit are separated so that the conduction from the lead 6 to the lead connecting the variable condenser 1 and the grid 2 shall not-be aifected by the influence of an ionization characteristic with respect to the plate 9 of the triode.

Asa possible alternative to the arrangement shown in Fig. 1, I provide, in- Fig. 2, a triode 3', in which a grid element 2, funct1on1ng partially as a hot cathode by means an exciting battery 14', is provided. Thus, by virtue ofthe two cathodic elements 2' and 7 the equivalent of an ionization v atmosphere will occur within the triode in such manner as to fulfill the requirements of.

.the De Forest soft-vacuum triode.

However, I do notwish it to be understood i that myinvention is limited, inits more general applications, to a shunting ;of the hard type of triode by means of an Edison valve having a soft vacuum. Thus, in Figs, 3 and 4, especially, I have shown two pos sible arrangements whereby a hard-vacuum tube' may be made to function'very much in the same manner as the grid element 2 acts toward the filament 7 in the triode 3'. By providing a hard type of Edison valve it is found necessary to attach one pole of the exciting battery 14 to the grid 2 of the triode, and the plate 15 of the control to the lead 6. In Fig. 4, in addition, I have provided an adjustable-voltage control 16 in the lead ductor 6. X

In the operation of my should be noted that the usua of adjustment with respect toa given uencyof signal should be made without any reference to the grid control. Thereafter, the batteries 14 or 14' are adjusted in order to invention, it

joining the plate 15 with theconobtain the right type of ionization effect with respect to the filament 7 of the triode. By this means, it will be found that a very marked improvement in the operation of the entire signalling system will be achieved.

While I have described and illustrated certain embodiments of my invention, it will be apparent to those skilled in the art that various changes, modifications, substitutions, additions and omissions may be made in the apparatus described without departing from the spirit and scope of the invention.

I claim as my invention:

1. In combination, a hard triode comprising an envelope containing a thermionic cathode, an anode and a grid arranged to emit electrons when heated, means for causing an electron flow within said envelope between said cathode and said plate, the grid being interposed in the path of said flow whereby it will acquire a negative charge,

a circuit external to said container including said grid and said cathode and comprising means for insulating said grid from said cathode, and means for heating said grid to temperatures at which it emits electrons, whereby an electron stream may be caused to flow from said grid to said cathode and the said negative charge controllably dissipated.

2. In combination with the grid, a plate, and a filament of a hard triode, means for producing an electronic stream between said filament and said plate, said grid lying in the path taken by said stream, and additional means including a potential source for heating said grid, whereby an electronic stream may be eontrollably produced in the reverse direction between said filament and said grid and the action of a soft triode may be simulated.

In testimony whereof, I have hereunto subscribed my name this 22nd day of June,

ABRAHAM PRESS. 

